Tensile strength fibres

Carbon fibre (%) Tensile strength (MPa) Flexural modulus (GPa) Izod notched impact (J/m)... 

In the succeeding examples, we shall deal with a h3rpothetical polymer being processed into fibres and the dependent variable is tihe fibre tensile strength. We shall make various modifications to this basic idea in an attempt to show how the various forms of analysis of variances are related to each other. After each form of this general example we shall deal in detail with another example of simijar structure. A number of aspects of the use of the analysis of variance follow in Chapter XII. 

The most useful parameters describing the fibres are length, length/diameter ratio (aspect ratio), fibre tensile strength and shape. In general, fibre length varies from 6 to 65 mm and the diameter varies from 0.5 to 1.0 mm. 

Treatment type Lignin removal Single fibre tensile strength (MPa) Composites tensile strength (MPa)... 

In every approach one finds a wide range of sophistication. In the continuum approach, the simplest (and most common) models are based on linear elastic fracture mechanics (LEFM), a well developed discipline that requires a linear elastic behaviour and brittle fracture, not always exhibited by fibres. Ductility and the presence of interfaces, not to mention hierarchical structures, make modelling much more involved. The same is true of the atomistic approach fracture models based on bond breaking of perfect crystals, using well established techniques of solid state physics, allow relatively simple predictions of theoretical tensile stresses, but as soon as real crystals, with defects and impurities, are considered, the problem becomes awkward. Nevertheless solutions provided by these simple models — LEFM or ideal crystals — are valuable upper or lower bounds to fibre tensile strength. 

Classification of fibre Tensile strength (MPa) Modulus of elasticity (GPa) Ultimate elongation (%)... 

Polymerisation of a diol with a dicarboxybe acid is exemplified by the production of a polyester from ethylene glycol and terephthabc acid either by direct esterification or by a catalysed ester-interchange reaction. The resulting polyester (Terylene) is used for the manufacture of fibres and fabrics, and has high tensile strength and resibency its structure is probably ... 

A unidirectional fibre composite consists of 60% by volume of continuous type-1 carbon fibres in a matrix of epoxy. Find the maximum tensile strength of the composite. You may assume that the matrix yields in tension at a stress of 40 MPa. 

Its = tensile strength parallel to fibres d] = fracture strength of fibres d = yield strength of matrix. 

Compared with nylon 66 fibres, the polyurethane fibres (known as Perlon U) have a tensile strength at the higher end of the range quoted for nylon 66, they are less prone to discolouration in air, are more resistant to acid conditions and they have a lower moisture absorption. On the debit side they are less easy to dye, are hard, wiry and harsh to handle and have too low a softening point for many applications. They are currently of little importance but have found some use in bristles, filler cloths, sieves and a few other miscellaneous applications. 

Spandex fibres, because of their higher modulus, tensile strength and resistance to oxidation, as well as their ability to be produced at finer deniers, have made severe inroads into the natural rubber latex thread market. They have also enabled lighter weight garments to be produced. Staple fibre blends with non-elastic fibres have also been introduced. 

As shown in Fig. 3.4 stress-strain tests on uniaxially aligned fibre composites show that their behaviour lies somewhere between that of the fibres and that of the matrix. In regard to the strength of the composite, Ocu, the rule of mixtures has to be modified to relate to the matrix stress, o at the fracture strain of the fibres rather than the ultimate tensile strength, o u for the matrix. 

Example 3.4 For the PEEK/carbon fibre composite referred to in Example 3.2 calculate the values of V j and Vent if it is known that the ultimate tensile strength of PEEK is 62 MN/m. ... 

The maximum value of it will occur when (tensile strength of the fibre, Ofu, and this is defined as the critical fibre length, Ic... 

A reinforced plastic sheet is to be made from a matrix with a tensile strength of 60 MN/m and continuous glass fibres with a modulus of 76 GN/m. If the resin ratio by volume is 70% and the modular ratio of the composite is 25, estimate the tensile strength and modulus of the composite. 

If the matrix in 3.7 was reinforced with the same volume fraction of glass but in the form of randomly oriented glass fibres rather than continuous filaments, what would be the tensile strength of the composite. The fibres are 15 mm long, have an aspect ratio of 1000 and produce a reinforcement efficiency of 0.25. The fibre strength is 2 GN/m and the shear strength of the interface is 4 MN/m". 

For fibres and filaments such orientation is desirable, but for solid objects where impact strength is often more important than tensile strength such orientation is usually unwelcome. It can also have further unwanted effects. This arises from the fact that oriented molecules are basically unstable and will at the first opportunity try to coil up. Thus on heating samples up to temperatures near severe distortion can occur leading to warped mouldings. 

A recent approach was based on the DMAc/LiCl and N-methyl-2-pyrrohdone/IiCl solvent systems [252,253] that enabled better dry tensile strengths although they did not provide adequate wet tenacities, due to poor crystallinity and poor consohdation of the fibre. A further problem was the... 

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